thanks for posting your query in HCM.. perioral dermatitis is named to skin disease that manifest as multiple papules pustules or vesicles found surrounding perioral skin and nasolabial folds.. it can be caused by many reasons like allergy to certain medication autoimmune disease nutritional deficiency habits like lip sucking or lip chewing or licking etc.. as u told that u have near corner of mouth it can also be due to dribbling of saliva at corner of mouth followed by infection most commonly by fungi candida... so i will suggest you to use anti fungal mouth ointment on corner of mouth and antiseptic mouthwash.. also take multivitamin supplements.. hydrocortisone use is limited to condition that are either allergic or autoimmune in nature with precaution to stop the drug gradually after improvement.. hope my advice will help you positively.. thanks Dr. Priyanka